The present invention relates to an organic photosensitive device for electrophotography, and also to a method of processing a raw substrate of the device, wherein the electrophotography employs a monochromatic coherent light such as the laser used as an illuminate for exposing a photosensitive drum in the laser beam printers.
The word "aluminum" in this specification includes its alloys.
The photosensitive devices for electrophotography comprise in general a conductive substrate which is made of aluminum or its alloy and covered with a photosensitive layer. Inorganic photoconductive materials such as selenium have been used widely as the material of the photosensitive layer, but nowadays they are being replaced with organic photosensitive devices (i.e., "OPC" devices). These organic devices are made from organic materials, are therefore advantageous in their higher film formability, their lighter weight and their lower manufacture cost.
Efforts have been made to improve the function and efficiency of the organic photosensitive devices. The so-called laminated type of such an organic device was recently proposed, which comprises a charge generating layer (abbr. "CGL") and a charge transmitting layer (abbr. "CTL").
The organic photosensitive device of laminated type is used to record thereon digital picture signals, and in one of the proposed systems, the surface of said device is scanned or swept by a laser beam so as to form an electrostatic latent image as in the laser-beam printers (abbr. "LBP"). Usually, a semiconductor laser which emits the laser beam having a wavelength of about 650-820 nm is employed in those systems.
The laser beam is however one of the coherent monochromatic light beams. A beam portion pierces a photosensitive layer to be reflected by the inner surface of an underlying substrate is thus likely to interfere with another beam portion reflected by the outer surface of the photosensitive layer. As a result, interference fringes are often produced on solid zones of a recorded image (especially of an intermediate gradational tone) to thereby cause an intolerable uneveness of density.
It was already proposed to reflect in a diffused manner the light beam incident upon the surface of a conductive substrate when it is exposed to the light. Such a proposal employs the liquid honing process (as shown in the Patent Laying-Open Gazette 50-98327, 1975), or the superfinishing process (ibid. 50-27496, 1975 ), in order to reduce the intensity of reflected light beam by making rough the substrate surface.
It is however difficult for such a measure to practically provide the substrate surface with a uniform roughness, because an overall undulation and/or local corrugations are produced to decrease the surface charge.